A woman, center, surrounded by media covers her mouth on her arrival at a hotel which is prepared for relatives or friends of passengers aboard a missing airplane, in Beijing, China Saturday, March 8, 2014. A Malaysia Airlines Boeing 777-200 carrying 239 people lost contact over the South China Sea early Saturday morning on a flight from Kuala Lumpur to Beijing, and international aviation authorities still hadn’t located the jetliner several hours later. (AP Photo/Andy Wong)

A woman, center, surrounded by media covers her mouth on her arrival at a hotel which is prepared for relatives or friends of passengers aboard a missing airplane, in Beijing, China Saturday, March 8, 2014. A Malaysia Airlines Boeing 777-200 carrying 239 people lost contact over the South China Sea early Saturday morning on a flight from Kuala Lumpur to Beijing, and international aviation authorities still hadn’t located the jetliner several hours later. (AP Photo/Andy Wong)

A woman cries at the arrival hall of the International Airport in Beijing, China, Saturday, March 8, 2014. Relatives and friends were arriving at Beijing airport for news after a Malaysia Airlines Boeing 777-200 was reported missing on a flight from Kuala Lumpur to Beijing Saturday. (AP Photo/Ng Han Guan)

ALTERNATE CROP OF XHG102 A woman cries at the arrival hall of the International Airport in Beijing, China, Saturday, March 8, 2014. Relatives and friends were arriving at Beijing airport for news after a Malaysia Airlines Boeing 777-200 was reported missing on a flight from Kuala Lumpur to Beijing Saturday. (AP Photo/Ng Han Guan)

Family members arrive at a hotel which is prepared for relatives or friends of passengers aboard a missing airplane, in Beijing, China, Sunday, March 9, 2014. Search teams across Southeast Asia scrambled on Saturday to find a Malaysia Airlines Boeing 777 with 239 people on board that disappeared from air traffic control screens over waters between Malaysia and Vietnam early that morning. (AP Photo/Vincent Thian)

This photo provided by Laurent Errera taken Dec. 26, 2011, shows the Malaysia Airlines Boeing 777-200ER that disappeared from air traffic control screens Saturday, taking off from Roissy-Charles de Gaulle Airport in France. The Malaysia Airlines Boeing 777-200 carrying 239 people lost contact with air traffic control early Saturday morning, March 8, 2014 on a flight from Kuala Lumpur to Beijing, and international aviation authorities still hadn’t located the jetliner several hours later. (AP Photo/Laurent Errera)

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KUALA LUMPUR, Malaysia (AP) â€” Two large oil slicks spotted Saturday by the Vietnamese air force offered the first sign that a jetliner carrying 239 people had crashed into the ocean after vanishing from radar without sending a single distress call.

An international fleet of planes and ships scouted the waters between Malaysia and Vietnam for any clues to the fate of the Malaysian Airlines Boeing 777, which disappeared less than an hour after taking off from Kuala Lumpur bound for Beijing.

The oil slicks sighted off the southern tip of Vietnam were each between 10 kilometers (6 miles) and 15 kilometers (9 miles) long, the Vietnamese government said in a statement.

There was no immediate confirmation that the slicks were related to Flight MH370, but the government said they were consistent with the kind of slick that would be produced by the jet’s two fuel tanks.

After the oil was spotted, authorities suspended the air search for the night. It was to resume Sunday. A sea search continued in the darkness, the airline said.

The jet’s disappearance was especially mysterious because it apparently happened when the plane was at cruising altitude, not during the more dangerous phases of takeoff or landing.

Just 9 percent of fatal accidents happen when a plane is at cruising altitude, according to a statistical summary of commercial jet accidents done by Boeing.

Malaysia Airlines CEO Ahmad Jauhari Yahya said there was no indication the pilots had sent a distress signal. That might mean that whatever trouble befell the plane happened so fast the crew did not have time to broadcast even a quick mayday.

The lack of a radio call “suggests something very sudden and very violent happened,” said William Waldock, who teaches accident investigation at Embry-Riddle Aeronautical University in Prescott, Ariz.

The plane was last inspected 10 days ago and found to be “in proper condition,” Ignatius Ong, CEO of Malaysia Airlines subsidiary Firefly airlines, said at a news conference.

Two-thirds of the jet’s passengers were from China. The rest were from elsewhere in Asia, North America and Europe.

Asked whether terrorism was suspected, Malaysian Prime Minister Najib Razak said authorities were “looking at all possibilities, but it is too early to make any conclusive remarks.”

Contributing to fears of foul play was word from foreign ministries in Italy and Austria that the names of two citizens listed on the flight’s manifest matched the names on two passports reported stolen in Thailand.

Italy’s Foreign Ministry said an Italian man who was listed as being a passenger, Luigi Maraldi, was traveling in Thailand and was not aboard the plane. It said he reported his passport stolen last August.

Austria’s Foreign Ministry confirmed that a name listed on the manifest matched an Austrian passport reported stolen two years ago in Thailand. It said the Austrian was not on the plane, but would not confirm the person’s identity.

A long wait for answers could lie ahead. Finding the wreckage of aircraft that go down over deep ocean waters can often take days. Locating and then recovering the flight-data and cockpit-voice recorders can take months or even years.

At Beijing’s airport, authorities posted a notice asking relatives and friends of passengers to gather at a nearby hotel to await further information. A woman aboard a shuttle bus wept, saying on a mobile phone, “They want us to go to the hotel. It cannot be good.”

Passengers’ loved ones were escorted into a private area at the hotel, but reporters were kept away. A man in a gray hooded sweatshirt later stormed